The research deals with the feasibility of an early start of a ramjet air intake using CFD analysis. For this purpose, a two-dimensional air inlet geometry with six (6) holes located on the compression surface (the lower wall of the intake) was chosen. A relatively large amount of mass flow has been sucked through these holes in order to compensate for the spillage flow, and obtain an early start. The particular intake geometry was designed for a flight Mach number of M=2.7. In order to start this intake (swallow the ‘normal shock wave’ by acceleration, the vehicle had to be accelerated up to M=4.6. Once the intake started, the vehicle could be decelerated to the design conditions. Only at M=2.6 the normal shock wave was thrown out, and the intake turned into an unstarted condition.
The study included CFD simulations at four different flight Mach numbers: 2.4, 2.6, 2.8 and 3.0 respectively. The starting condition of each simulation was the original geometry of the intake with no open holes. The number of open holes was sequentially increased at each step until all the six holes were opened. When all six holes were open the intake started at all four Mach numbers. However, when closing the holes one at a time, and returning to the original configuration, the intake remained started for the cases of M=2.8 and M=3.0 but the normal shock was re-expelled to the front of the intake (unstarted intake) for the M=2.6 and M=2.4 cases.
